Structural and conformational changes in myocardial and erythrocyte actin during cardiac ischemia.

Structural and conformational changes in myocardial and erythrocyte actin during cardiac ischemia were studied by the method of fluorescence resonance energy transfer with highly selective fluorescent probes. In contrast to 15-min coronary artery occlusion, 120-min ischemia was accompanied by irreversible structural and conformational changes in the small domain of erythrocyte actin. Posttranslational changes during myocardial ischemia concerned the N- and C-terminal regions of actin and went beyond the allowed conformational fluctuations in the actin molecule without breaking the energy barrier.

Subcellular and molecular mechanisms of the effects of cardiac glycosides and angiotensin-converting enzyme inhibitors on contractile function and energy conversion in myocardial myofibrils under normal conditions and during acute cardiac insufficiency.

Experiments on skinned and hybrid myocardial fibers isolated from normal dogs and animals subjected to 120-min occlusion of the anterior interventricular branch of the coronary artery showed that in contrast to cardiac glycosides, angiotensin-converting enzyme inhibitors suppress contractile ability of myocardial myofibrils in a dose-independent manner within the concentration range of 10(-12)-10(-4)M. This effect is accompanied by a decrease in fiber relaxation rate most pronounced in the presence of captopril. Actin, the major protein of fine filaments is the target for b-acetyldigoxin, K-strophanthin, captopril, enalapril, and trandolapril in myocardial myofibrils.

Electron microscopy of the complexes of ribulose-1,5-bisphosphate carboxylase (Rubisco) and Rubisco subunit-binding protein from pea leaves.

The structure of ribulose-1,5-bisphosphate carboxylase (Rubisco) subunit-binding protein and its interaction with pea leaf chloroplast Rubisco were studied by electron microscopy and image analysis. Electron-microscopic evidence for the association of Rubisco subunit-binding protein, consisting of 14 subunits arranged with 72 point group symmetry, and oligomeric (L8S8) Rubisco was obtained.

[Various parameters of the structure of F-actin filaments of the normal and athyreotic myocardium].

A comparative analysis of optical diffraction of electron micrographs of F-actin from normal and athyreosic myocardia showed abrupt changes of relative intensities of the reflexes nearest to the meridian in the athyreosic actin pattern. It indicates that under athyreosis changes in the actin globules or in their location in the fibril take place.